Epitaxy is a process that is used extensively in semiconductor processing to form very thin material layers on semiconductor substrates. These layers frequently define some of the smallest features of a semiconductor device. The epitaxial material layers may also have a high quality crystal structure if the electrical properties of crystalline materials are desired. A deposition precursor is normally provided to a processing chamber in which a substrate is disposed and the substrate is heated to a temperature that favors growth of a material layer having desired properties.
It is generally desired that the thin material layers (film/s) have very uniform thickness, composition, and structure. Because of variations in local substrate temperature, gas flows, and precursor concentrations, it is quite challenging to form films having uniform and repeatable properties. The processing chamber is normally a vessel capable of maintaining high vacuum, typically below 10 Torr. Heat is normally provided by heat lamps positioned outside the vessel to avoid introducing contaminants into the processing chamber. Pyrometers or other temperature metrology devices may be provided to measure the temperature of the substrate.
Control of substrate temperature, and therefore local layer formation conditions, is complicated by thermal absorptions and emissions of chamber components and exposure of sensors and chamber surfaces to film forming conditions inside the processing chamber. In addition, providing substantially equal amounts of radiation across the substrate surface is another challenge when attempting to form thin material layers having a low thickness variation (a high degree of uniformity) across the surface of the substrate.
Therefore, there is a need in the art for a radiation system and lamphead array having improved radiation uniformity control and thermal processing capabilities.